Electrical rectifier



June 27, 1944. R, OVERHOLT, JR 2,352,283

ELECTRICAL RECTIFIR Filed May 28, 1942 2 Sheets-Sheet 2 5 51x A y 19 dit? 19 I2 L l L.; l l :im E

fg 'n nl :if ::Ii Y u: 133.31 .'20 Q 20 2'0 22 142 15 n n 10m @4 j f @j Malzep 00p/01919 l5 Cappel Oxide duoed Coppel Patented June 27, 1944 Ralph Overholt, Jr., Da

Switch and v vale, Pa., a (corporation The Union yton, Ohio, assignor'to Signal Company, Swissof Pennsylvania Appl'icationgMay 2s, 1942, seria1N6.444,7s7

10 Claims. (Cl. 175-366) My invention relates to electrical rectiers, and particularly to electrical rectifiers of the wellknown copper oxide type.

. When copper oxide rectifier elements are manufactured from thin copper, it is desirable to oxiaccomplishing this desirable .according to my invention, the elements after on one side only.

`I shall describe three forms of rectfiers embodying my invention and one method for prenovel features thereof in claims.v

In the accompanying drawings, Fig. l is a View in exaggerated form, a rectifier element as it appears in certain steps in the proc-y Figs. 4 and 5 are top and bottom views,

y vice employed in a portion of ess of manufacture embodying my invention.

tively, showing a completed rectifier element contaken on the lines VI-VI and VII-VII, respectively, 0f Fig. 4. Figs. 8, 9 and 10 are top plan, vertical sectional, and side elevational views, respectively, of a masking deone. process of manufacture embodying my invention. Fig. l1 is a top plan view showing a modified form of rectier element as it appears in one step of the process embodying my invention. Fig. 12 is a sectional view taken on the line XII-XII of Fig. 13 is a. view of processes of manufacture also Vention.

Similar reference characters refer to similar parts in each of the several views.

embodying my incircular configuration. central aperture I, although this particular form isnot essential to my invention. The blank A after being cleaned in any suitable manner, as

black oxide of copper.

After the oxidation is completed the oxidized blank, which I shall hereinafter refer to as a rec tier element, is treated to remove the cupric oxide layer from the entire surface of the element. This treatment may take a variety of forms, but

acid and .1 per cent by volume of hydrochloric acid in water. The temperature at which the solution is used is not critical, desired action of the solution is materially speeded up if the solution is hot preferably at a temperature of 80 to 100 C. With an 80 C.

2 solution. the element is preferably immersed in the solution for a time interval which is approximately twice as long as is required to remove the cupric oxide. After the element has been immersed in the solution for the desired period of time, it is then removed from the solution, washed in water, and thoroughly dried..

The element is nextpreferably immersed for a I short period of time (of the order of one to three,

that the copper oxide surface will be sumciently clean for. certain subsequent steps which shouldv preferablyl be performedA before the element has hadlany-chance toaccumulate any foreign substances either from the atmosphere or otherwise.

The element following this step will'appear ass illustrated in Fig, 3 in which D designates the cuprous oxide remaining on the element. It should be particularly noted that as shown in Fig. 3 there is a clean cut discontinuity between the cuprous oxide and the mother copper at the inside and outside edges of the element onV both sides ofthe element. This is desirable for a purpose whichwill be made clear presently.

The portion of thev process-of manufacture of the element thus far described is well known, and.'

differs from that described in detaily in Letters Patent of the United States No. 2,094,642'grantedY to Philip H. Dowling on October 5, 1937; for the Manufacture of electrical rectifiers only in that the blank A is initially oxidized on both sides.-

According to my present invention, the element is next treated to provide it with a metal layer or coating which makes Contact with the'- oxide layer only on one side of the element, and" with both the oxide layer and the mothercopper on the opposite side of the element. The metal coating can be obtained ina variety of ways as willnow-be made clear.

One method by which the desired coating canv be obtained consists in reducing certain portionsl of the outer surface of the copper oxide to metallic copper and then plating the reduced portions with a suitable metal, suchas nickel. On

the side ofthe element on which'the junction of' the oxide coating with the mother copper is to be used for rectification, which side I shall hereinafter referl to for convenience as the rectifyingl side, the reduced portion preferably consists yoi an annular area designated alv in Figs. 6 and?,

which area is separated or spaced from the ad'- jacent inner and outer exposed edges ofthe mother copper by non-reduced annular areas designated a2 and a3, respectively, in Figs. 6 and '7. The non-reduced portions need be only wide enough to preclude any possibility of electrical contact being established with the mother copper by the reduced copper on this side of the element, and with the well-known inchand a half washer, the non-reduced areas, may for example be ,a of an inch in width. Onv the oppositie side of the element. which side I shall hereinafter refer to as the non-rectifying side, the

entire surface of the oxide may be reduced although for convenience in accomplishing the reduction it may be desirable to leave certain areas` to Philip H. yDowling and John D;

. may be readily separated.

7 the rubber sheet causes non-reduced for a reason which will appear presently. For Apurposes of myl present invention'. it is only necessary that a suiiicient portion be reduced so that if all ofthe reduced portion is subsequently plated, the good contact with the mother copper at at least one point and will provide alarge enough contact area and sufficient lateral conductivity to establish a satisfactory contact with the. mother cop-v per if a contact washer or either side of a similar element is clamped against the element. The reduction and plating may be accomplished elec,- trolytically in the manner described in Letters Patent ofthe United States No. 2,197,632, granted McCluer on August 16, 1940, except for the fact that in carrying out the reduction and plating it is necessary to use a masking means which is different from that shown in the patent. A suitable form of masking means is shown in Figs. 8; 9 and 10.

Referring tov Figs. 8. 9 and 10, the masking means here shown comprises` two blocks 3 and 4 of insulating material clamped together by bolts provided with wing, nuts 6, whereby the blocks The lower blockz3' is formed with a central circular opening T'havi'ng a diameter equal to the desired outside diameter of'the contact metal which isto be applied to the rectifying side of the element, and the upper' block 4f is provided with an aligned opening 8 of the same diameter as `the opening Tsurrounch eds'by a plurality of projections'orV teeth 9;; The blocks are separated by aA sheet I0 of rubber, neoprene, or the like cemented ory otherwise secured to the upper face of the lower block 3. and this il which has I and 8,' and sheet is provided with an opening the same diameter as the openings which aligns vertically with these openings. The element to be processed is disposed between the block 4 and the rubber sheet. I0 in concentric relation' to the openings 1f, 8l and II with the rectifying side facing the block 3i; andv is, em-A beddedinto the sheet i0:by pressure:appliedv by the teeth 9; The embedding of the elementslnto it to iiow'upv around'the outer lower edge of. the element'asufiicient distance to seal or mask the mother copper against the action of the'elec'- trolyte during. the reducing andl plating steps.

`The teeth 9 are radiallydisposed', andareof-such lengths that the portion of the upper outer edge of the mother copper between each two adjacent teeth will be exposedI to the action of the electrolyte.

A bridging member I2'. of insulating material.

is secured at its ends to the lower. side of.; the b1ock3 by means of machine'screws I3.'and spacing members I4'; and this bridgingmember, is

provided with a central., circular legA I5 which' projects upwardlyinto the openingA 1 in the block.

3; This leg `is concentric with the opening TV and is provided in its upper end. with a cupped recessl I6 which receives the rounded lower end' IIv'of a corresponding leg I8 provided onV a bridgingk member I9 secured by means of screws 20'.and

spacing members 2l to the upperv block I. Thel leg I5 is also provided at its upper grid with a rubber washer 22l cemented or otherwise secured.

thereto, which washer engages the underside of` the rectifier element A and'which has ancutside diameter equal to the desired'inside diameter-of the contact metal4 which is to be applied. tothe rectifyinrr side of the element. A correspondingy washer 23 is secured to a shoulder 24 which sur'-4 rounds the rounded lower end il ofthe log I8,

plating will establish the exposedlower edge. of

and the lower sideof 'thiswasher carries .ametal ring 25 in such manner that .when the two blocks 3 and 4 .are secured together, this ring will be .pressed into engagement with the upper inside exposed edge of the mother copper. This ring is connected to a wire 2.6, whereby external electrical contact may vreadily be established with the mother copper of the element during the reducing and platingsteps. The parts are so proportioned that when the element is in place in the mask, the washer 22 will .engage the lower inside edge of the element and effectively mask the engaged area from the action of the electrolyte.

It will be understood that in the reducing and vplating steps the mask with the element in place will be inserted bodily into the reducing or plating bath as the cathode, and current will be passed to the element through the bath from a suitable anode. As was pointed out hereinbefore, the reducing and plating steps may be carried out as described in United States Patent No. 2,197,632, and if a full description of these steps is desired reference may be had to this patent. The completed element will appear as shown in Figs. 4, -5, 6 and '7 described hereinbefore.

If desired, the contact between the metal ring 25 and the mother copper of the element may be improved by reaming out the hole I in the element. Furthermore, the contact between the mother copper and the contact metal on the nonrectifying side can be improved by removing small areas of the copper oxide fromy the non-rectifying side, by etching or otherwise, to expose the mother copper as shown .in Figs. v11 and 12.

Another method by which the desired coating can be obtained consists in masking the exposed inside and outside edges ofV the mother copper and adjacent areas of the oxide coating on one side of the element, and then depositing by vaporization and condensation or cathodic sputtering a layer of metal such as gold or silver. Other metals such as aluminum, zinc, cadmium or copper may be applied in a similar manner. The vaporization or sputtering of the metal may be accomplished by well-known methods, and it is believed tcbe unnecessary, therefore, .to describe these methods herein. Since the vaporized or sputtered metal appears to travel in straight' lines, a simplified form of mask such as that shown in Fig.. 13 may be used. As here shown, this mask consists of two concentric washers 30 and 3|. The one washer 30 is provided in its inside edge with an annular recess 30a having a depth equal to about half the thickness of the element, and an outside diameter which is just large enough to snugly receive the outside edge of the element, while the other washer is provided in its outside edge with an annular recess 31a having approximately the same depth as the recess 30a, and .an inside diameter which will permit the inside edge of the element to enter the recess with a relatively snug fit. The two washers 30 and 3| are fitted over the inside and outside edges of the element as shown in Fig. 13, and the metal is applied rst to one side and then the other. It will be obvious that the metal applied to the upper side as viewed in Fig. 13 wil1 Contact both the upper oxide layer and the mother copper as shown .in Fig. 14, While the metal applied to the lower or rectifying side will contact the oxide layer only ata central annular area.

A third method by which the desired coating can be applied includes spraying of the contact metal. Preferably in this latter method the outer surface ,of the oxide is first reduced to copper at all portions which are to be coated. This Vreduction may, for example, be accomplished `electrolytically in the manner described in connection with ythe first method set forth hereinbefore. During the spraying step, the edges of one side of the element should be masked, and for this purpose the mask shown in Fig. 13 may be employed. The completed element will appear as shown yin Fig. 15.

Although I have herein shown and described only three forms of rectifiers embodying my invention, it is understood that various changes and modifications vmay be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. As a new article of manufacture, a Copper oxide rectifier comprising a copper blank oxidized on both sides to prevent warping and coated on one side with a metallic coating which contacts the mother copper to facilitate making contact with the mother copper.

r2. The method of making a copper oxide recti der element which consists in oxidizing a copper 'blank on both sides, treating it to expose the mother copper at an edge of the blank, and then short circuiting the oxide coating on one side of the blank by applying a metal coating which contacts the mother copper at at least one exposed point.

3. The method of making a copper oxide rectier element which consists in oxidizing a copper blank on both sides to prevent it from warping, chemically treating the blank to form a clear cut discontinuity between the oxide coating and the mother copper at the edges of the blank, and then coating one side of the blank with a metal which contacts the mother copper at at least a part of one edge.

4. As a new article of manufacture, a copper oxide rectier comprising a copper blank oxidized on both sides to prevent warping and coated on both sides with a metal coating, the metal coating on one side being in contact with the oxide layer only to facilitate making electrical contact therewith and the coating on the other side being in contact with both the oxide layer and with the mother copper to facilitate making contact with the mother copper.

5. The method of making contact with the mother copper and with one oxide surface of a copper-cuprous oxide rectier element which has been oxidized on both sides that comprises chemically treating the element to expose the mother copper at the edges of both sides of the element, masking the exposed-edges and an adjacent area of the oxide surface on one side of the element, reducing the exposed oxide surface to copper, and plating the reduced copper surface with another metal.

6. The method of making contact with the mother copper and with one oxide surface of a copper-cuprous oxide rectifier element which has been oxidized on both sides that comprises chemically treating the element to expose the mother copper at the edges of both sides of the element, masking the exposed edges and an adjacent area of the oxide surface on one side of the element. and then applying to the non-masked surface another metal which contacts the oxide only on the masked side and which contacts both the oxide and the mother copper on the opposite side.

7. The method oi' making contact with the mother copper and with one oxide surface of a copper-cuprous oxide rectiner element which has been oxidized on both sides that comprises chemically treating the element to expose the mother copper at the edges of both sides of the element, masking the exposed edges and an adjacent area of the oxide surface on one side of the element, and then applying to al1 of the non-masked surface of the element by vaporization and condensation a layer of metal to establish Contact with the oxide layer only on one side of the ele ment and with the mother copper on the opposite side of the element. l

8. The method of making contact with the mother copper and with one oxide surface of a copper-cuprous oxide rectifier element which has been oxidized on both sides that comprises chemically treating the element to expose the mother copper at the edges of both sides of the element, masking the exposed edges and an adjacent area of the oxide surface on one side of the element, and then applying to all of the non-masked surface of the element by cathodic sputtering a layer of metal to establish contact with the oxide layer only on one side of the element and with the.

mother copper on the opposite side of the element.

9. The method of making contact with the mother copper and with one oxide surface of a copper-cuprous oxide rectifier element which has been oxidized on both sides that comprises chemically treating the element to form a clear cut discontinuity between the oxide and the mother copper of the element at the edges of the element. removing small Iareas of the copper oxide on one side of the element to expose the mother copper, said areas being insulcient in size to cause warpage, masking the exposed edges of the mother copper and an adjacent area of the oxide surface onV the other side of the element, and then applying to al1 of the non-masked surface of the element a layer of contact metal to establish contact with the mother copper on said one lside of the element and with the oxide layer only `,spraying the reduced copper surface with another metal which contacts the reduced copper only on the masked side of the element and both the reduced copper and the mother copper on the other side of the element.

RALPH OVERHOLT, J n. 

